For ArcGIS 8.1

If the files are incompatible when you install, you'll receive a message. If you install something after ArcGIS 8.1 that updates either incorrectly, you may encounter the following error upon trying to start the applications (e.g. ArcMap or ArcCatalog):

Compatible versions

The compatible versions of these dlls installed by Microsoft Windows NT are:

Comcat.dll version 4.71 and Ole32.dll version 4.0

To determine the version of these dlls on your machine, right click on the file names (e.g., Comcat.dll and Ole32.dll), located under c:\WINNT\system32, click on Properties, and click on the Version tab.

If you do not have version 4.71 of Comcat.dll, you will need to install it.